final tweaks to meal plan

src/main/java/mi/hdm/exceptions/InvalidMealPlanException.java

+package mi.hdm.exceptions;
+
+public class InvalidMealPlanException extends RuntimeException {
+    public InvalidMealPlanException(String message) {
+        super(message);
+    }
+}

src/main/java/mi/hdm/mealPlan/MealPlan.java

 package mi.hdm.mealPlan;
 
+import mi.hdm.exceptions.InvalidMealPlanException;
 import mi.hdm.recipes.NutritionCalculator;
 import mi.hdm.recipes.NutritionTable;
 import mi.hdm.recipes.Recipe;
@@ -8,6 +9,7 @@ import org.apache.logging.log4j.Logger;
 
 import java.time.LocalDate;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 
 /**
@@ -18,6 +20,11 @@ public class MealPlan {
     private final Map<LocalDate, Recipe> plan;
 
     public MealPlan(Map<LocalDate, Recipe> plan) {
+        if (!plan.isEmpty()) {
+            if (plan.keySet().stream().anyMatch(Objects::isNull))
+                throw new InvalidMealPlanException("The specified map is invalid (null key)");
+        }
+
         this.plan = plan;
     }
 
@@ -26,10 +33,8 @@ public class MealPlan {
             throw new NullPointerException("Date can not be null");
         }
 
-        LocalDate invalid = LocalDate.now().plusDays(7);
-
-        if (date.isBefore(LocalDate.now()) || invalid.isBefore(date)) {
-            throw new UnsupportedOperationException("You can only add recipes between today and in 7 days from now!");
+        if (!isDateValid(date)) {
+            throw new InvalidMealPlanException("You can only add recipes between today and in 7 days from now!");
         }
         plan.put(date, recipe);
     }
@@ -38,6 +43,7 @@ public class MealPlan {
         if (date == null) {
             throw new NullPointerException("Date can not be null");
         }
+
         if (plan.containsKey(date)) {
             log.info("Day {} cleared successfully.", date);
             plan.remove(date);
@@ -70,4 +76,8 @@ public class MealPlan {
         return NutritionCalculator.calculateNutritionTable(this);
     }
 
+    private boolean isDateValid(LocalDate date) {
+        LocalDate invalid = LocalDate.now().plusDays(7);
+        return !(date.isBefore(LocalDate.now()) || invalid.isBefore(date));
+    }
 }

src/test/java/mi/hdm/mealPlan/MealPlanTest.java

 package mi.hdm.mealPlan;
 
+import mi.hdm.exceptions.InvalidMealPlanException;
 import mi.hdm.recipes.Recipe;
 import mi.hdm.recipes.ValidObjectsPool;
 import org.junit.jupiter.api.BeforeEach;
@@ -22,6 +23,14 @@ class MealPlanTest {
         underTest = new MealPlan(new HashMap<>());
     }
 
+    @Test
+    public void shouldNotInitializeWithInvalidMap() {
+        //given
+        LocalDate date = LocalDate.now();
+
+        assertThrows(NullPointerException.class, () -> underTest = new MealPlan(Map.of(null, recipeOne, date, recipeTwo)));
+    }
+
     @Test
     public void canAddToMealPlan() {
         //given
@@ -47,8 +56,8 @@ class MealPlanTest {
         LocalDate past = LocalDate.of(2000, 1, 1);
 
         //expect throw
-        assertThrows(UnsupportedOperationException.class, () -> underTest.addRecipeToMealPlan(recipeOne, future));
-        assertThrows(UnsupportedOperationException.class, () -> underTest.addRecipeToMealPlan(recipeOne, past));
+        assertThrows(InvalidMealPlanException.class, () -> underTest.addRecipeToMealPlan(recipeOne, future));
+        assertThrows(InvalidMealPlanException.class, () -> underTest.addRecipeToMealPlan(recipeOne, past));
     }
 
     @Test